The advantages of rack and pinion steering for vehicles have long been recognized. Steering precision and reduction in objectionable steering forces are among those advantages for which rack and pinion steering units are utilized. Rack and pinion steering is particularly desirable in high performance vehicles.
In a typical rack and pinion steering unit according to the prior art, an elongated flat rack is engaged with a pinion gear. The steering shaft is connected to the pinion gear so that steering movements are converted into rotation of the pinion gear and a reciprocal translation of the rack. The rack is normally horizontal and is connected at its outer ends through tie rods and steering arms to the wheels of the vehicle. In many applications, the position of the steering unit is considerably above the terminus of the steering arm so that the resulting tie rods are relatively short and angulated upwardly to connect between the steering arm and rack ends. As the vehicle negotiates an uneven surface, such as in off-road racing, the steered wheels of the vehicle move through the full range of vertical travel permitted by the suspension system. Because of the short and highly angulated tie rods, vertical travel of the wheel causes an undesired steering movement of the wheel. These steering movements degrade the performance of the vehicle and introduces objectionable feedback forces through the steering unit and steering shaft to the steering wheel and driver. At high speeds, this so-called bump steering effect can make it extremely difficult to maintain control of the vehicle.
Therefore, it is desirable to have a rack and pinion steering unit that reduces the undesired steering movements of the steered wheels of the vehicle during vertical suspension movements and reduces undesirable feedback forces transmitted to the driver. Such a steering unit is particularly desirable where it is compact and sufficiently strong to withstand hard use.